Widgets may be produced by the consolidation of material utilizing a variety of different techniques. A number of prior art techniques confine the material which is to be consolidated within a die, can or mold; and then subject the material to sufficient temperature and pressure to effect consolidation into the desired bulk object. If the material to be consolidated is of such a composition that it will react in a detrimental manner with the atmosphere, it may be necessary to hermetically seal the material in a container prior to consolidation. If the material is hermetically sealed without first evacuating the container absorbed gas and other contaminants will be sealed in the container. Therefore, when elevated temperature consolidation is preformed on materials that needed to be hermetically sealed within a container an opening is provided for removal of the entrapped gases and/or high vapor pressure contaminants prior to sealing and consolidation. Gaseous contaminants can be removed by heating the material, since heating will cause the partial pressure of the gaseous contaminants to increase and then flow through any opening in the container. If a reduction in entrapped gas pressure greater than that which can be achieved by heating is required, a vacuum can be applied to the container opening to assist in reduction of gas pressure.
One of the specific techniques utilized for elevated temperature consolidation is Hot Isostatic Pressing (HIP). Material that is to be consolidated by HIP is first contained in a can in which an opening is provided for removal of gaseous contaminants. Prior to consolidation the can is heated and/or subjected to a reduced pressure to remove entrapped gases and high vapor pressure contaminants. After removal of gaseous contaminants the can is hermetically sealed. The can containing the particulate is then subjected to sufficient temperature and isostatic pressure to effect the desired consolidation.
A variety of fluid die processes are also used to consolidate material into bulk shapes. As with the HIP can, the fluid die may be provided with a sealable opening for degassing.
One of the current processes utilizing fluid dies is Rapid Omnidirectional Compaction (ROC). Prior to ROC consolidation the material to be consolidated is contained within a fluid die. The fluid die is then heated to a temperature such that the mold material will respond as either a plastic compressible fluid, a plastic incompressible fluid or an elastomeric solid. The material contained within the fluid die yields under the consolidation pressure. ROC utilizes conventional forging equipment, such as hydraulic or mechanical presses to apply sufficient pressure to cause yield of the material and effect consolidation. One of the primary advantages of the ROC process is that the pressure is applied at a rapid rate and therefore only a short dwell time at elevated temperature is required. ROC is further described in U.S. Pat. Nos. 4,094,709, 4,233,720 and 4,142,888.
The above described prior art techniques require that the material which is to be consolidated be confined within a container; that gaseous contaminants be removed from the container; that the container then be sealed; and finally that the container be heated to the appropriate consolidation temperature. After the container is sealed the portion of the wall in the vicinity of the evacuation opening will have different deformation characteristics. This has meant that a truly uniform hydrostatic pressure could not be applied to the material since the container had inhomogeneities in the wall.
U.S. Pat. No. 4,104,782 teaches a method of providing a container for HIP which has a wall of uniform character. The container of the '782 patent is formed by applying a porous coating to a preform. The coating can be applied using any of a variety of conventional techniques including flame and plasma spraying. Since the coating of the '782 patent when applied is porous gas can flow through the coating when the coated preform is heated and/or subjected to a vacuum. The coating of the '782 patent is of such a composition and structure that the coating will densify and become non-porous and pressure-tight at elevated temperature. In this manner a container can be formed which has a wall of uniform character and does not require a separate operation of heating, evacuating and sealing prior to HIP.
U.S. Pat. No. 4,212,669, which is a continuation-in-part of the '782 patent, teaches forming a two layer porous coating as shown in FIG. 1 on a preform that is to be consolidated by HIP. As with the coating of the '782 patent, the coating of the '669 patent is initially porous and at the conclusion of the degassing operation the coating becomes non-porous and pressure-tight. In the method of the '669 patent the inner layer 10 serves as a barrier layer to prevents diffusion of the coating into the material 12 that is to be consolidated. During the heating associated with degassing the outer layer 14 densifies and thereby becomes non-porous and pressure-tight prior to HIP as shown in FIG. 2.
Another method of forming a container having walls of uniform character is taught in U.S. Pat. No. 3,992,200. The container of the '200 patent is formed by applying a porous coating of uniform character to a preform. The coated preform of the '200 patent is then placed in a container which is filled with particulate. The particulate is composed of a first inert pressure transfer media and a secondary reactive pressure transfer media. To effect consolidation the coated preform is heated and pressure is applied to the coated preform through the pressure transfer media. During consolidation gaseous contaminants will flow from the porous preform through the porous coating and react with the secondary reactive pressure media. The '200 patent suggests using for the secondary pressure media particles of a reactive metal such as titanium, zirconium or hafnium. The coating of the '200 patent differs from the coating of the '782 and '669 patents in that the coating of the '200 patent does not lose its porous character.
An object of the present invention is to provide a multi-piece can for containment of material during consolidation, such can having walls which are initially semipermeable and prior to consolidation become nonpermeable.
An object of the present invention is to provide a continuous can for containment of material which is to be consolidated by the application of pressure at elevated temperature, such can having initially semipermeable walls which prior to consolidation seal by reaction or interaction to become nonpermeable.
Another object of the present invention is to provide a can for containment of cast ingots during the application of sufficient temperature and pressure to heal ingot cracks.
Another object of the present invention is the production of a seamless or multi-piece seamed can having walls made from flat powder.
These and other objects of the present invention will become apparent from the following description, figures and examples.